Boulogne-sur-Mer (French pronunciation: [bu.lɔɲ.syʁ.mɛʁ], Latin: Gesoriacum or Bononia, Dutch: Bonen) is a city in Northern France. Boulogne lies on the Côte d'Opale, a tourist coast on the English Channel.

Boulogne was the major Roman port for trade and communication with Britain. After a period of Germanic presence following the collapse of the Empire, Boulogne was at the centre of an eponymous county of the Kingdom of France during the Middle Ages, and was occupied by the Kingdom of England numerous times due to conflict between the two nations.

The city's 12th-century belfry is recognised by UNESCO as a World Heritage Site, while another popular attraction is the marine conservation centre, Nausicaa.

In the Middle Ages Boulogne was the capital of an eponymous county, founded in the mid-9th century. An important Count, Eustace II, assisted William the Conqueror in his conquest of England. His wife founded the city's ⊙Notre Dame cathedral, which became a site of pilgrimage from the 12th century onwards, attended by fourteen French kings and five of England. It was an important whaling center prior to 1121, but in time the gray whale became extinct in the Atlantic and the few surviving right whales were inadequate to be profitable. The city survived on herring fishing and received its municipal charter from Count Renaud of Dammartin in 1203.

The area was fought over by the French and the English, including several English occupations during the course of the Hundred Years War. Boulogne was again occupied by the English from 1544 to 1550. In 1550, The Peace of Boulogne ended the war of England with Scotland and France. France bought back Boulogne for 400,000 crowns. A culture of smuggling was present in the city until 1659, when French gains in Flanders from the Treaty of the Pyrenees moved the border northwards.

Boulogne received its current status as a subprefecture of the Pas-de-Calais department in 1800 due to the territorial re-organisation in Revolutionary France. Three years later, it was given the title of an Imperial City (Ville Impériale).

The 19th century was a prosperous one for Boulogne, which became a bathing resort for wealthy Parisians after the completion of a railway line to the French capital. In the 19th century, the Basilica of Notre-Dame de Boulogne was reconstructed by the priest Benoit Haffreingue, who claimed to have received a call from God to reconstruct the town's ruined basilica.

Sights

Boulogne's 12th century belfry is one of 56 in northeastern France and Belgium with shared World Heritage Site status. It is the oldest building in the upper city, and currently serves as the home to a museum of Celtic remains from the Roman occupation. Founded as the Counts' dungeon, the top floor was added in the 13th century. Damage by a fire in 1712 was built over by 1734.

⊙ Cathedral basilica of Notre-Dame, with a dome standing at over 100 m. The crypt is one of the largest in France, and has Roman, Romanesque and Gothic elements.

⊙ Opened in 1991, Nausicaä - The French National Sea Centre is a science centre entirely dedicated to the relationship between mankind and the sea. It houses Aquaria, exhibitions on the marine fauna, and the exploitation and management of marine resources (fisheries, aquaculture, coastal planning, maritime transport, exploitation of energies and mineral, tourism).

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